Designing Kitchens and Bathrooms - HardieBacker Installation

Gutted and remodeling my entire backroom and I am at the stage now where all the new greenboard is up and it's time to put up the HardieBacker around the bathtub.

I have heard different suggestions regarding putting up a vapor barrior behind the HardieBacker in the bathtub area. I checked HardieBacker's site and the recommended installation instructions for walls and it makes no mention of a vapor barrior behind.

Any thoughts/opinions on if I should do or not do and if so, what material (heard roofing felt, 6 mil dropcloth, etc.)

Thanks

:thinker: i have never used a vapor barrier behind hardibacker. really don't see why you would need it? put up hardybacker, seal joints and tile.? i'm sure someone will give you a better answer.

If you have half the walls up already, it's pointless to install a barrier. This is usually done prior to any walls.

Tar paper or poly sheeting should line the studs and overlap the flange of the receptor. This is your waterproofing. No, it's not really a vapor barrier, it's a moisture barrier. The exception to the rule is when a topical waterproofer is used. It's one or the other but not both.

Here's a little test anyone can do. Take a piece of your favorite cbu, hardi, durock, whatever. Take a tupperware (don't let your wife see you) and cut out the bottom. Silicone it to the cbu and let it cure. Once cured, fill it with water. Do this while your significant other is sleeping and hold it over their head. Then time how long before they wake up from the Chinese water torture and beat you.

This is what goes on behind the walls when no barrier is used. ;)

Thanks all...HotinOKC, I meant to say the rest of the walls in the bathroom are newly put up (greenboard) but the walls surrounding the tub are still down to the studs. I left that for last and the HardiBacker.

Tilebri, thanks for the advice. That paints a pretty good picture. Moisture barrier it is then.

Any adivce on what to use. Like I said I have heard others who have said they use roofing felt or 6 mil dropcloth but would rather have a more definitive answer.

Thanks again!!

4-6 mil Poly is used. DON'T buy one of those flimsy plastic drop clothes at a Big Box and expect it to be 4 or 6 mil poly, they are about .05 mil poly.:)

ALL cement backerboards require a moisture barrier if a topical waterproofing is not being used.:wall:

4-6 mil Poly is used. DON'T buy one of those flimsy plastic drop clothes at a Big Box and expect it to be 4 or 6 mil poly, they are about .05 mil poly.:)

ALL cement backerboards require a moisture barrier if a topical waterproofing is not being used.:wall:

Thanks Bud...6 mil poly it is then.

Thanks agan!

4-6 mil Poly is used. DON'T buy one of those flimsy plastic drop clothes at a Big Box and expect it to be 4 or 6 mil poly, they are about .05 mil poly.

Crap, I got so wrapped up in my little tupperware experiment I let out the thickness. Sheesh, I've typed it so many times, the fingers are supposed to automatically do it.

Crap, I got so wrapped up in my little tupperware experiment I let out the thickness. Sheesh, I've typed it so many times, the fingers are supposed to automatically do it.

No worries Tilebri...I wouldn't use anything but 6 mil. Will be putting up the HardiBacker this weekend in the bathtub area.

On their site, they recommend Latex or Acrylic modified thinset to fill the joints but underneath that it also says type 1 mastic. I have heard that I should NOT use Mastic anywhere where water will be present. Thinset is the play for the joints on the HardiBacker around the bathtub, correct. Then 2" wide high-strength alkali-resistant glass fiber tape?

Thanks for the assistance. Since you all are the professionals, it really helps me out in doing it right the first time!